1. Field of the Invention
The present invention relates to a liquid discharge head (usually, called an ink jet recording head) that performs the recording or printing of characters, marks, images, or the like by discharging a functional liquid, such as ink, processing liquid for fixing ink, among some others, to a medium that bears recorded images, including paper, plastic sheet, cloths, and some others. The invention also relates to a liquid discharge apparatus that uses such liquid discharge head, and to a method for manufacturing the liquid discharge head as well.
2. Related Background Art
As a liquid discharge apparatus, there is the liquid discharge apparatus that records images by use of the liquid discharge head that discharges ink by utilization of thermal energy provided by heat generating element.
Conventionally, as a liquid discharge head of the kind, there has been the liquid discharge head which is structured by mounting a plate 7 having thereon an ink flow path 4 and ink discharge port 16 on the circumference of a base plate 8 having thereon a heat generating element 3 for bubbling use installed for discharging ink if the portion surrounding the ink discharge port is observed in an enlargement as shown in FIG. 13, for example.
For the liquid discharge head of the kind, various printing capabilities, such as higher image quality, higher resolution, and higher speed, are more in demand increasingly, among some others, necessitating the further provision of multiple nozzle arrangement, and finer liquid droplets as well.
However, with the aforesaid conventional structure as shown in FIG. 13, there are the problems to be encountered as given below.
For the conventional liquid discharge head as shown in FIG. 13, the area of the heat generating element for bubbling use is made smaller to make the bubbling energy smaller accordingly for obtaining finer liquid droplets to attain a higher resolution, while making the area of discharge port smaller to obtain a desired amount of discharge at a desired discharge speed. However, if the discharge port is made smaller, the viscosity of ink tends to become higher on the interfacial portion of the discharge port between ink and the air outside if the discharge interval is caused to be longer for that one particular discharge port, although there is no problem as far as discharges are made continuously all the time. If this condition takes place, discharge becomes impossible eventually, and there is a problem of disabled discharges. Also, with finer liquid droplets, a larger amount of liquid should be discharged at a higher speed to compensate for the smallness of each liquid droplet, and the air outside is drawn at the interfacial portion between ink and the air outside on the discharge port at the time of debubbling. As a result, it takes a long time to stabilize the interfacial portion thereof. This makes it difficult to repeat an extremely high frequency of discharges.
The present invention is designed under such circumstances as described above. It is an object of the invention to provide a liquid discharge head capable of discharging finer liquid droplets even at longer intervals of discharges, and also, capable of increasing the discharge speed of liquid droplets, thus making the repetition of discharge frequency extremely high, while meeting the demand that increases more for the arrangements of multiple nozzle, higher speed, and finer liquid droplets for the liquid discharge head. It is also an object of the invention to provide a liquid discharge apparatus that uses such head, and a method for manufacturing the liquid discharge head as well.
In order to achieve the above objects, the liquid discharge head of the present invention is structured as shown in the paragraphs (1) to (11); the liquid discharge apparatus as in the paragraph (12); and the method for manufacturing the liquid discharge head as in the paragraphs (13) to (22) given below.
(1) A liquid discharge head comprises a discharge energy generating device for generating energy to be utilized for discharging liquid as drops, and a discharge port arranged to face the discharge energy generating device. For this head, the area of the discharge port is smaller than the area of the discharge energy generating device, and the discharge port is arranged in the liquid.
(2) For the liquid discharge head referred to in the preceding paragraph (1), the opening portion, which holds an interface for liquid and the air outside to be in contact, is provided to face the discharge port, and the area of the opening portion is larger than the area of the discharge port.
(3) For the liquid discharge head referred to in the preceding paragraph (2), one opening portion is arranged for a plurality of discharge ports.
(4) For the liquid discharge head referred to in the paragraph (1), the distance from the front edge of the discharge port to the interface for liquid and the air outside to be in contact is within a range of 2 xcexcm to 20 xcexcm.
(5) For the liquid discharge head referred to in the paragraph (1), the liquid flow path is arranged corresponding to the discharge energy generating device for supplying liquid onto the discharge energy generating device.
(6) For the liquid discharge head referred to in the paragraph (1), the discharge port formation wall surrounds the space from the surface of the discharge energy generating device to the discharge port.
(7) For the liquid discharge head referred to in the preceding paragraph (6), the liquid flow path is arranged corresponding to the discharge energy generating device for supplying liquid onto the discharge energy generating device.
(8) For the liquid discharge head referred to in the preceding paragraph (7), the opening portion, which holds the interface for liquid and the air outside to be in contact, is arranged in a position facing the discharge port.
(9) For the liquid discharge head referred to in the preceding paragraph (8), the area of the opening portion is larger than the area surrounded by the edge portion of the outer wall of the discharge port formation wall on the discharge port side.
(10) For the liquid discharge head referred to in the paragraph (7), the height of the discharge port formation wall and the height of the liquid flow path wall for forming the liquid flow path are the same.
(11) For the liquid discharge head referred to in the paragraph (1), the liquid discharge head discharges liquid as drops by creating film boiling in liquid by thermal energy generated by the discharge energy generating device.
(12) A liquid discharge apparatus, which mounts thereon a liquid discharge head referred to in the paragraph (1) for discharging liquid as drops from the liquid discharge head for the adhesion thereof to a recording medium, comprises carrying means for conveying the recording medium.
(13) A method for manufacturing a liquid discharge head, which is provided with a discharge energy generating device for generating energy to be utilized for discharging liquid as drops; a discharge port arranged in the liquid to face the discharge energy generating device; a liquid flow path arranged corresponding to the discharge energy generating device for supplying liquid onto the discharge energy generating device; a discharge port formation wall surrounding the space from the surface of the energy generating device to the discharge port; and a liquid flow path wall for forming the liquid flow path, the area of the discharge port being smaller than the area of the discharge energy generating device facing the discharge port, comprises the step of forming the discharge port formation wall and the liquid flow path wall by semiconductor manufacturing process altogether on the base plate having the discharge energy generating device arranged therefor.
(14) For the method for manufacturing a liquid discharge head referred to in the paragraph (13), the semiconductor manufacturing process comprises the steps of preparing a base plate having the discharge energy generating device arranged therefor; forming an etching stop layer in a position facing the lower part of the space from the surface of the discharge energy generating device on the base plate to the discharge port; laminating film becoming material of the discharge port formation wall or the liquid flow path wall on the base plate and the etching stop layer; forming an etching mask layer in a position on the film facing the discharge port formation wall or the liquid flow path wall; forming the discharge port formation wall and the liquid flow path wall altogether by etching the film; and
removing the etching stop layer and the etching mask layer.
(15) For the method for manufacturing a liquid discharge head referred to in the paragraph (13), the discharge port formation wall and the liquid flow path wall are formed by silicon nitride, silicon oxide, or silicon carbide.
(16) For the method for manufacturing a liquid discharge head referred to in the paragraph (13), the discharge port formation wall and the liquid flow path wall are formed by photosensitive resin.
(17) For the method for manufacturing a liquid discharge head referred to in the preceding paragraph (16), the photosensitive resin is a thin film formed by spin coating method on a base plate having the discharge energy generating device mounted thereon.
(18) For the method for manufacturing a liquid discharge head referred to in the paragraph (16), photosensitive resin film is adhesively bonded in the form of film to form the liquid flow path on the discharge port formation wall and the liquid flow path wall.
(19) A method for manufacturing a liquid discharge head, whack is provided with a discharge energy generating device for generating energy to be utilized for discharging liquid as drops; a discharge port arranged in the liquid to face the discharge energy generating device; a liquid flow path arranged corresponding to the discharge energy generating device for supplying liquid onto the discharge energy generating device; an opening portion positioned to face the discharge port and hold an interface for liquid and the air outside to be in contact; a discharge port formation wall surrounding the space from the surface of the energy generating device to the discharge port; a liquid flow path wall for forming the liquid flow path; and an opening portion forming member for forming the opening portion, the area of the discharge port being smaller than the area of the discharge energy generating device facing the discharge port, and the area of the opening portion being larger than the area surrounded by the edge portion of the outer wall on the discharge port side of the discharge port formation wall for forming the discharge port confronted by the opening portion, comprises the step of forming the discharge port formation wall, the liquid flow path wall, and the opening portion forming member by semiconductor manufacturing process on a base plate having the discharge energy generating device arranged therefor.
(20) For the method for manufacturing a liquid discharge head referred to in the preceding paragraph (19), the semiconductor manufacturing process comprises the steps of preparing a base plate having the discharge energy generating device arranged therefor; forming on the base plate a first film becoming the material of the lower part of the discharge port formation member or the material of the lower part of the liquid flow path wall; removing a part of the first film to form the lower part of the discharge port formation member and the lower part of the liquid flow path wall altogether; forming a second film becoming the material of the upper part of the discharge port formation member or the material of the upper part of the liquid flow path wall on the lower part of the discharge port formation member and the lower part of the liquid flow path wall so as to cover the base plate; removing a part of the second film to form the upper part of the discharge port formation material and the upper part of the liquid flow path wall altogether; forming a third film becoming the material of the opening portion forming member on the upper part of the discharge port formation member and the upper part of the liquid flow path wall so as to cover the base plate; and removing a part of the third film to form the opening portion forming member.
(21) For the method for manufacturing a liquid discharge head referred to in the paragraph (19), the opening portion forming member is formed by photosensitive resin plate.
(22) For the method for manufacturing a liquid discharge head referred to in the preceding paragraph (21), the photosensitive resin plate is a film in the form of film adhesively bonded onto the liquid flow path wall.